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The binding of a viral pathogen to the host cell is the first, crucial, step of infection. This first step in host-pathogen interactions is dependent on the attachment tools of the viral pathogen and the presentation of attachment factors by the host. Pathogen receptor specificity and host receptor distribution govern which cells and tissues are susceptible, known as host tropism. Using our own developed tissue microarrays to represent the host and the viral attachment proteins to represent the pathogen, we set out to study how receptor-binding interactions can improve our understanding of receptor distribution of both domestic and wild animals and how glycobiology plays a key role in driving these receptor-binding interactions. We used these tools to study and map the receptor binding of influenza A & D attachment proteins in respiratory tissues of various domesticated and wild animals. Receptor binding is the first step in infection and it is therefore of high importance to study it. The use of tissue microarrays is a great in-between system for studying the distribution of these host receptors. The system does have its shortcomings, particularly in terms of glycolipid and mucin detection. To summarize, TMAs are not a replacement for current methods used, such as glycan arrays and animal experiments, but are an excellent addition that complements those systems for studying receptor interactions.

The binding of a viral pathogen to the host cell is the first, crucial, step of infection. This first step in host-pathogen interactions is dependent on the attachment tools of the viral pathogen and the presentation of attachment factors by the host. Pathogen receptor specificity and host receptor distribution govern which cells and tissues are susceptible, known as host tropism. Using our own developed tissue microarrays to represent the host and the viral attachment proteins to represent the pathogen, we set out to study how receptor-binding interactions can improve our understanding of receptor distribution of both domestic and wild animals and how glycobiology plays a key role in driving these receptor-binding interactions. We used these tools to study and map the receptor binding of influenza A & D attachment proteins in respiratory tissues of various domesticated and wild animals. Receptor binding is the first step in infection and it is therefore of high importance to study it. The use of tissue microarrays is a great in-between system for studying the distribution of these host receptors. The system does have its shortcomings, particularly in terms of glycolipid and mucin detection. To summarize, TMAs are not a replacement for current methods used, such as glycan arrays and animal experiments, but are an excellent addition that complements those systems for studying receptor interactions.

The binding of a viral pathogen to the host cell is the first, crucial, step of infection. This first step in host-pathogen interactions is dependent on the attachment tools of the viral pathogen and the presentation of attachment factors by the host. Pathogen receptor specificity and host receptor distribution govern which cells and tissues are susceptible, known as host tropism. Using our own developed tissue microarrays to represent the host and the viral attachment proteins to represent the pathogen, we set out to study how receptor-binding interactions can improve our understanding of receptor distribution of both domestic and wild animals and how glycobiology plays a key role in driving these receptor-binding interactions. We used these tools to study and map the receptor binding of influenza A & D attachment proteins in respiratory tissues of various domesticated and wild animals. Receptor binding is the first step in infection and it is therefore of high importance to study it. The use of tissue microarrays is a great in-between system for studying the distribution of these host receptors. The system does have its shortcomings, particularly in terms of glycolipid and mucin detection. To summarize, TMAs are not a replacement for current methods used, such as glycan arrays and animal experiments, but are an excellent addition that complements those systems for studying receptor interactions.

Glycans, also known as carbohydrates, are an essential component of all living organisms and are, among other things, present on proteins and lipids in the cellular membrane. Glycan structure is not encoded in the genome, oppose to other biopolymers such as RNA and proteins, but is regulated by around 200 glycosyltransferase enzymes. As a result of substrate competition, glycans are generated that vary in composition, linkage positions and configurations. The large heterogeineity and diversity in glycan structure complicates the synthesis and characterization of glycans. The research described in this dissertation covers the synthesis of well-defined glycans and applies synthetic glycans in the development of analytical methodology for the detailed structural characterization of naturally occuring glycans. Chemically modified glycans are synthesized by employing glycosyltransferase enzymes. These modifications are manipulated to (de)activate certain positions on a glycan and thereby direct glycosyltransferase activity. Traceless removal of these modifications allows the synthesis of complex natural glycans with controlled architecture. These glycans are used to study differences in biological activity between isomeric glycans. Synthetic glycopeptides with various functionalities are used as model substrates to develop a method to release glycans from glycopeptides without damaging the glycan structure itself. This methodology conserves labile glycan modifications that are often lost in glycan analysis. Furthermore, synthetic complex glycans are applied as reference compounds for the development of analytical methodology that can structurally elucidate challenging glycan epitopes.

Glycans, also known as carbohydrates, are an essential component of all living organisms and are, among other things, present on proteins and lipids in the cellular membrane. Glycan structure is not encoded in the genome, oppose to other biopolymers such as RNA and proteins, but is regulated by around 200 glycosyltransferase enzymes. As a result of substrate competition, glycans are generated that vary in composition, linkage positions and configurations. The large heterogeineity and diversity in glycan structure complicates the synthesis and characterization of glycans. The research described in this dissertation covers the synthesis of well-defined glycans and applies synthetic glycans in the development of analytical methodology for the detailed structural characterization of naturally occuring glycans. Chemically modified glycans are synthesized by employing glycosyltransferase enzymes. These modifications are manipulated to (de)activate certain positions on a glycan and thereby direct glycosyltransferase activity. Traceless removal of these modifications allows the synthesis of complex natural glycans with controlled architecture. These glycans are used to study differences in biological activity between isomeric glycans. Synthetic glycopeptides with various functionalities are used as model substrates to develop a method to release glycans from glycopeptides without damaging the glycan structure itself. This methodology conserves labile glycan modifications that are often lost in glycan analysis. Furthermore, synthetic complex glycans are applied as reference compounds for the development of analytical methodology that can structurally elucidate challenging glycan epitopes.

Glycans, also known as carbohydrates, are an essential component of all living organisms and are, among other things, present on proteins and lipids in the cellular membrane. Glycan structure is not encoded in the genome, oppose to other biopolymers such as RNA and proteins, but is regulated by around 200 glycosyltransferase enzymes. As a result of substrate competition, glycans are generated that vary in composition, linkage positions and configurations. The large heterogeineity and diversity in glycan structure complicates the synthesis and characterization of glycans. The research described in this dissertation covers the synthesis of well-defined glycans and applies synthetic glycans in the development of analytical methodology for the detailed structural characterization of naturally occuring glycans. Chemically modified glycans are synthesized by employing glycosyltransferase enzymes. These modifications are manipulated to (de)activate certain positions on a glycan and thereby direct glycosyltransferase activity. Traceless removal of these modifications allows the synthesis of complex natural glycans with controlled architecture. These glycans are used to study differences in biological activity between isomeric glycans. Synthetic glycopeptides with various functionalities are used as model substrates to develop a method to release glycans from glycopeptides without damaging the glycan structure itself. This methodology conserves labile glycan modifications that are often lost in glycan analysis. Furthermore, synthetic complex glycans are applied as reference compounds for the development of analytical methodology that can structurally elucidate challenging glycan epitopes.

This thesis focuses on two approaches from the interdisciplinary field of chemical biology. The first approach is related to glycobiology. Glycans are present on the surface of all cells, also on bacteria. Since these molecules are on the cell surface, they are often the first to interact with the environment and therefore also play an important role in many host-microbe interactions. An illustrative example of their importance is glycan mimicry of host glycans by bacteria, by which bacteria can interact with host receptors or avoid immune recognition by the host. An overview of bacteria that display glycan mimicry and chemical biology techniques to study this occurrence are presented in this thesis. In general, the study of glycans is ideally suited for chemical biology. The first chemical biology approach of this thesis describes two techniques to introduce N-acetylneuraminic acid on bacterial glycans: selective exoenzymatic labeling (SEEL) and native sialyltransferases. These new techniques could contribute to elucidating the interaction between sialylated bacterial pathogens and the immune system. It also highlights the promising future of glycoengineering for the study of bacterial glycobiology. The second chemical biology approach of this thesis focuses on a screen of small molecules that induce a biological process somatic embryogenesis in plants. In this process, a somatic cell is reprogrammed and can grow into a new embryo after the addition of a chemical inducer, compound 2,4-D. A structure-activity relationship of 2,4-D was established based on a screen of a library of 2,4-D analogues. This research contributed to understanding the role of 2,4-D and stress in the process of somatic embryogenesis in plants. Both approaches described in this thesis show that chemical biology is a powerful approach to study and influence biological processes on the molecular level.

This thesis focuses on two approaches from the interdisciplinary field of chemical biology. The first approach is related to glycobiology. Glycans are present on the surface of all cells, also on bacteria. Since these molecules are on the cell surface, they are often the first to interact with the environment and therefore also play an important role in many host-microbe interactions. An illustrative example of their importance is glycan mimicry of host glycans by bacteria, by which bacteria can interact with host receptors or avoid immune recognition by the host. An overview of bacteria that display glycan mimicry and chemical biology techniques to study this occurrence are presented in this thesis. In general, the study of glycans is ideally suited for chemical biology. The first chemical biology approach of this thesis describes two techniques to introduce N-acetylneuraminic acid on bacterial glycans: selective exoenzymatic labeling (SEEL) and native sialyltransferases. These new techniques could contribute to elucidating the interaction between sialylated bacterial pathogens and the immune system. It also highlights the promising future of glycoengineering for the study of bacterial glycobiology. The second chemical biology approach of this thesis focuses on a screen of small molecules that induce a biological process somatic embryogenesis in plants. In this process, a somatic cell is reprogrammed and can grow into a new embryo after the addition of a chemical inducer, compound 2,4-D. A structure-activity relationship of 2,4-D was established based on a screen of a library of 2,4-D analogues. This research contributed to understanding the role of 2,4-D and stress in the process of somatic embryogenesis in plants. Both approaches described in this thesis show that chemical biology is a powerful approach to study and influence biological processes on the molecular level.

This thesis focuses on two approaches from the interdisciplinary field of chemical biology. The first approach is related to glycobiology. Glycans are present on the surface of all cells, also on bacteria. Since these molecules are on the cell surface, they are often the first to interact with the environment and therefore also play an important role in many host-microbe interactions. An illustrative example of their importance is glycan mimicry of host glycans by bacteria, by which bacteria can interact with host receptors or avoid immune recognition by the host. An overview of bacteria that display glycan mimicry and chemical biology techniques to study this occurrence are presented in this thesis. In general, the study of glycans is ideally suited for chemical biology. The first chemical biology approach of this thesis describes two techniques to introduce N-acetylneuraminic acid on bacterial glycans: selective exoenzymatic labeling (SEEL) and native sialyltransferases. These new techniques could contribute to elucidating the interaction between sialylated bacterial pathogens and the immune system. It also highlights the promising future of glycoengineering for the study of bacterial glycobiology. The second chemical biology approach of this thesis focuses on a screen of small molecules that induce a biological process somatic embryogenesis in plants. In this process, a somatic cell is reprogrammed and can grow into a new embryo after the addition of a chemical inducer, compound 2,4-D. A structure-activity relationship of 2,4-D was established based on a screen of a library of 2,4-D analogues. This research contributed to understanding the role of 2,4-D and stress in the process of somatic embryogenesis in plants. Both approaches described in this thesis show that chemical biology is a powerful approach to study and influence biological processes on the molecular level.